Compound semiconductor device have been known, wherein source, drain, and gate electrodes are formed over a compound semiconductor stacked structure.
Particularly, semiconductor devices made from nitride semiconductors, typically GaN, AlN, InN, and mixed crystals thereof, have become a focus of attention as higher-output electronic devices and shorter-wavelength light-emitting devices, for their superior material properties.
Field-effect transistors, particularly high electron mobility transistors (HEMTs), have been researched and developed in recent years as candidate higher-output electronic devices, and their applications to higher-output and highly-efficient amplifiers, high-power switching devices, and the like, have been sought for.